HUMAN SKIN
Skin acts as the first line of defense .
Following properties of it's outer surface makes it an effective barrier:
1.Acidic pH,
2.low moisture
3. Secretion of a peptide antibiotic named defensin.
But larvae of some parasites penetrate the intact skin to get access to our system. Besides, there can be invisible cuts present on our skin that helps them to get inside.
More to this,some parts of our skin like that of armpit and between legs contain high moisture leading to easy growth of microbes and their easy access to our system.
Structure and function of skin-
Skin consists of 2 parts: epidermis and dermis which rest on the subcutaneous fat layer .
Epidermis- it is the thin outer portion composed of several layers of epithelial cells.the outermost portion of skin is dead known as STRATUM CORNEUM.it contains a waterproof protein called KERATIN.
It forms an effective barrier to the entry of microbes.
Dermis-it is inner thick portion of the skin and is composed of connective tissues. Hair follicles,oil glands and sweat glands are present in dermis that can act as passages to the entry of microbes.
NOTE-Perspiration through Sweat glands,though contains nutrients and moisture for microbial growth but they contain salt at the same time which inhibits their growth. It also contain lysozyme.
Sebum secreted by oil glands contains UFA,proteins and salt which, though, nutritive but is inhibitory to the microbial growth at the same time.
NORMAL MICROBIOTA OF THE SKIN-
The surface of our skin is inhospitable to growth of a variety of bacteria and yet satsfying for lot others.reason being that these bacteria can grow in presence of salt and are resistant to drying.
Some aerobic bacteria produce fatty acids from sebum which inhibits the growth of others and help them flourish .
They tend to make clumps so that even vigorous washing can only reduce their number and not eliminate them.they remain in hair follicles and sweat glands and soon reestablish theirselves .
Body odor-areas of the body with high moistures like armpits and the region between legs contain high moisture and microbes present there metabolize the secretions of sweat glands contributing to body odor.
Acne-acne is caused by propionobacterium acne which is a type of diptheroids.they grow on sebum produced by oil glands and make propionic acid which lowers the pH of skin to 3 to 5 and contributes to acne.
Dandruff- dandruff is causef by an yeast named malassezea furfur which grows on sebum and makes skin scaly.shampoos treating dandruff contain KETOCONAZOLE, ZINC PYRITHIONE, SELENIUM SULFIDE which act against yeasts.
Skin acts as the first line of defense .
Following properties of it's outer surface makes it an effective barrier:
1.Acidic pH,
2.low moisture
3. Secretion of a peptide antibiotic named defensin.
But larvae of some parasites penetrate the intact skin to get access to our system. Besides, there can be invisible cuts present on our skin that helps them to get inside.
More to this,some parts of our skin like that of armpit and between legs contain high moisture leading to easy growth of microbes and their easy access to our system.
Structure and function of skin-
Skin consists of 2 parts: epidermis and dermis which rest on the subcutaneous fat layer .
Epidermis- it is the thin outer portion composed of several layers of epithelial cells.the outermost portion of skin is dead known as STRATUM CORNEUM.it contains a waterproof protein called KERATIN.
It forms an effective barrier to the entry of microbes.
Dermis-it is inner thick portion of the skin and is composed of connective tissues. Hair follicles,oil glands and sweat glands are present in dermis that can act as passages to the entry of microbes.
NOTE-Perspiration through Sweat glands,though contains nutrients and moisture for microbial growth but they contain salt at the same time which inhibits their growth. It also contain lysozyme.
Sebum secreted by oil glands contains UFA,proteins and salt which, though, nutritive but is inhibitory to the microbial growth at the same time.
NORMAL MICROBIOTA OF THE SKIN-
The surface of our skin is inhospitable to growth of a variety of bacteria and yet satsfying for lot others.reason being that these bacteria can grow in presence of salt and are resistant to drying.
Some aerobic bacteria produce fatty acids from sebum which inhibits the growth of others and help them flourish .
They tend to make clumps so that even vigorous washing can only reduce their number and not eliminate them.they remain in hair follicles and sweat glands and soon reestablish theirselves .
Body odor-areas of the body with high moistures like armpits and the region between legs contain high moisture and microbes present there metabolize the secretions of sweat glands contributing to body odor.
Acne-acne is caused by propionobacterium acne which is a type of diptheroids.they grow on sebum produced by oil glands and make propionic acid which lowers the pH of skin to 3 to 5 and contributes to acne.
Dandruff- dandruff is causef by an yeast named malassezea furfur which grows on sebum and makes skin scaly.shampoos treating dandruff contain KETOCONAZOLE, ZINC PYRITHIONE, SELENIUM SULFIDE which act against yeasts.
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